DE102009052263B4 - Fiber composite material, production of a textile fabric for this purpose, and components produced therefrom and their use - Google Patents

Abstract

Sheet-like member (20), at least partially made of a fiber composite material having a matrix and fibers embedded in the matrix in the form of at least one textile fabric (12, 14), wherein a part of the line formations (14 ) has an increased mechanical damping capacity compared to the remaining line formations (12), characterized in that the line formations (14) with the increased mechanical damping capacity are provided only in certain component surface areas (22) or in these component area areas (22) have a significantly higher proportion own than in other component surface areas.

Description

The present invention relates to a fiber composite material having a matrix and fibers which are embedded in the matrix in the form of at least one textile fabric made of textile line formations. Furthermore, the invention relates to components made of such a fiber composite material and their use, as well as a method for producing the textile fabric.

The term "textile line structure" here generally refers to an elongated (in particular quasi-endless) structure formed from one or more fibers. This includes in particular any type of yarn or thread as well as a so-called "roving", ie a bundle of quasi-endless, untwisted fibers.

The term "textile fabric" refers generally to an extensively extended structure made from such line formations. In particular, it includes any type of tissue, braid or scrim.

For producing a fiber-reinforced component (fiber composite component), it is known to prefabricate a textile fabric produced in this way as a semifinished fiber material and this semifinished product by infiltration with initially liquid or viscous matrix material (eg synthetic resin) and subsequent hardening (eg thermally) to the fiber composite component further processing.

Fiber composite materials are used as a construction material in many areas of industry. The advantages include the high specific (weight) stiffness and strength and the high energy absorption capacity. Mutual interactions between the matrix and the fibers embedded therein give a fiber composite superior properties than any of the two components involved individually.

In many applications, there is a need for a fiber composite material or a component produced therefrom, which has particularly good mechanical damping properties, such as to reduce vibration and / or radiated sound during use in correspondingly vibration or sound installation environments (eg aircraft).

A currently common procedure for increasing the damping of fiber composite materials is the subsequent application of damping coatings. However, this means an additional step in production. Frequently, more intermediate steps are required, such. As the tailoring of damping pads to measure, as they often can not be laid over a full area of a flat expanded fiber composite material due to other installations or recesses. In d1er production of sheet-like components, eg. As panels, the often considerable Picke a required damping lining is often a serious drawback in practice, because thus the required space is increased accordingly and additional weight is required.

The paper "Dipa Ray et al: Modification of the Dynamic Dampening Behavior of Jute / Vinyl Ester Composites with Latex Interlayer, in: Composites, Part B 38 (2007), pages 380-385" is about attempts to increase the internal damping of a jute / Vinylester fiber composite reported by incorporation of intermediate layers of latex-coated Jutelagen in the base material (jute / vinyl ester composite). The disadvantage here, however, in addition to the manufacturing effort for the production and introduction of the additional damping layers on the one hand, the non-continuous improvement of the damping properties (in the whole volume) and on the other hand, the risk of delamination of the layer structure at the interfaces created in the matrix.

The publication AT 47 560 E describes a reinforcing element intended to be embedded in a resin in the form of a web of reinforcing fibers oriented in at least one direction.

From the publication DE 697 32 664 T2 For example, a triaxial braided sleeve is known which includes first skein strands extending in a first helical direction, second skein strands extending in a second helical direction different from said first helical direction, and axial reinforcing strands.

It is an object of the present invention to provide a way to improve the mechanical damping properties of fiber composite materials of the type mentioned above and components produced therefrom, in particular a simple production of flat-extended components should be made possible without adversely increasing their space requirements.

According to a first aspect of the invention, there is provided a sheet member at least partially made of a fiber composite material having a matrix and having fibers embedded in the matrix in the form of at least one textile fabric made of textile linear structures, a part of the line structures being compared to the rest of the lines has increased mechanical damping capacity, thereby characterized in that the line formations are provided with the increased mechanical damping capacity only in certain component surface areas or in these component surface areas have a much higher proportion than in other component surface areas.

The basic idea of the invention is therefore to increase the internal damping of the fiber composite material by introducing additional textile line structures which possess increased mechanical damping capacity into the textile fabric (or by replacement of a part of the conventional textile line structures by more strongly attenuating textile line structures in the textile fabric). ,

The invention thus makes it possible in a simple manner to increase the internal damping of weakly attenuated fiber composite materials.

With the proportion provided according to the invention (up to 50%) of line structures of increased mechanical damping capacity, vibrations and radiated sound can advantageously be reduced when using the fiber composite material or a component produced therefrom. The production of the fiber composite material requires in practice no significant additional effort. In the production of the textile fabric which is required in any case, only a part of the line structure used for this purpose is to be replaced by the line structure of an increased mechanical damping capacity. Advantageously, so that the inner damping of the material can be continuously improved. In addition, no disadvantageous interfaces are created within the matrix.

In a preferred embodiment, the fabric is a woven fabric, a braid or a scrim.

The lines of increased mechanical damping capacity, also referred to below as "damping threads" for the sake of simplicity, can be interwoven, interlaced or laid directly with the remaining line formations, also referred to below as "reinforcing threads" for the sake of simplicity.

Among other things, vibrations and structure-borne noise in such a textile fabric produce shearing movements which are efficiently damped by the introduced damping threads, for example by additional friction between the existing threads and / or by damping in the material of the damping threads. As a result, a reduction in the surface speed and thus a reduction of the radiated sound can be expected.

The damping threads as well as the reinforcing threads can z. B. each be designed as a yarn or thread or as a roving. The cross-section of each damping thread can basically be chosen arbitrarily, but is preferably circular or rectangular (eg strip-shaped roving).

With regard to the choice of the fiber material of the reinforcing threads and of the matrix material can be used advantageously known per se materials or combinations of materials.

Suitable fibers for the reinforcing threads are, for example, glass fibers, carbon fibers, synthetic synthetic fibers (for example aramid fibers), steel fibers or natural fibers.

In one embodiment, it is provided that the reinforcing threads are formed from glass fibers, carbon fibers or aramid fibers.

As a matrix material, in particular plastics such. As thermosetting plastics (resins) interesting. In a preferred embodiment, it is a matrix based on epoxy resin.

In one embodiment, it is provided that the damping threads are formed from fibers which have an increased density and / or an increased elasticity and / or a viscous or viscoelastic property (in each case as compared to the material of the fibers of the reinforcing threads).

In this regard, for example, the damping yarns may each comprise elastic fibers of a crosslinked polymer (e.g., rubber, latex, etc.), e.g. B. of natural or synthetic rubber, or consist exclusively of such fibers.

In one embodiment, it is provided that the damping threads are formed from synthetic fibers, for. Example, melt spun fibers made of an elastic polymer.

In a polymer for producing the damping threads may be in particular a thermoplastic such. As polyurethane, polyamide, etc. act.

The damping threads can z. B. as a web of elastic fibers or as a mixed swirl with a significant proportion of elastic fibers (eg more than 30%, in particular more than 50%) to be made.

The damping threads can z. B. be formed as a twisted yarns, as twisted yarns are usually more elastic than untwisted yarns.

Depending on the material density and amount of damping threads used, the mass of a component according to the invention thus produced may increase, but this is beneficial to the desired advantage of vibration damping or sound insulation.

The component can be used as a structural or non-structural structural component of a technical device such as in particular z. B. a vehicle (including aircraft) may be provided. To further increase the damping, the component according to the invention can also be vapor-deposited with additionally attached (eg glued) damping mats (eg made of rubber, latex, etc.).

In particular, with the invention, a planar component, for. B. a panel can be produced. This means in particular components in which the square root of the component surface at least 5 times, in particular at least 10 times as large as the component thickness (or, where appropriate, average component thickness) is. In many applications, such as for soundproofing panels in aircraft, the component thickness in the range of 0.5 to 3 cm, in particular in the range of 1 to 1.5 cm are, and the component surface z. B. be greater than 1 m ² .

In particular, such a panel z. B. in the ceiling area of helicopter cabins are used, since there are the main noise sources (engine and transmission).

According to the invention, it is provided that damping threads are present in at least one component region, whereas in at least one other component region no or a significantly smaller proportion of damping threads are provided. This advantageously takes into account the fact that the formation as well as the propagation of vibrations or sound in a specific application environment of the component generally does not take place homogeneously or isotropically. For an effective damping while at the same time the least possible impairment of the component strength can thus be carried out according to this development, a local adaptation of fiber composite properties to the specific application.

So z. B. by targeted introduction (eg., Weaving) of damping threads only in one or more portions of the component, the dynamic behavior of the component structure can be changed or optimized.

In the case of a planar component, partial surfaces of the component with the additional damping threads replacing the conventional reinforcing threads can bring about a locally higher mechanical impedance in the component structure. The appropriate provided at a higher mechanical impedance may, for. B. be used to reflect introduced vibrations or structure-borne noise and / or channeling or complicating the forwarding.

The partial surface or the partial surfaces which are provided with the damping threads (or are provided with a significantly higher proportion of damping threads) may be provided inside a component surface and / or directly at the edge of the component surface.

The integration of damping threads in the edge region of flat components is also of particular interest because in many applications (eg interior panels of aircraft) such components are provided on their side edges with a supporting structure (eg so-called stringers and / or frames of a Fuselage). Although z. B. in the case of an inner panel of an aircraft, such a connection with the main structure is often done via so-called "shockmounts", Velcro or the like, then a according to the invention in the edge region equipped with damping threads panel an outgoing from the main structure entry harmful or unwanted vibrations further complicate in the panel. The effect here can essentially be attributed to the increased impedance jump. In the case of aircraft, an airborne sound path from the aircraft exterior structure via an air gap to an interior panel is often already combated with sound-absorbing or sound-insulating mats, but due to the connection of the panel edges there is still potential for structure-borne noise transmission. However, such structure-borne sound paths can be hindered efficiently by an inventive design of damping component edges.

Another application of the development described above, according to which the damping threads are provided only in certain component areas or have a significantly higher proportion in these areas (eg, at least twice as large proportion), the damping of modal natural oscillations of the component, for. B. a plate. For this purpose, the integration of the damping threads z. B. preferably be provided on the antinodes or the fast maxima. The location of such maxima in a component or on a component surface of a panel can, for. B. are already determined during construction or at least estimated (eg by finite element analyzes). Alternatively or additionally, such maxima or other suitable locations in or on the structure may be determined experimentally or estimated (eg, by spatially resolved vibration measurements).

The fiber composite material according to the invention can have the damping threads in a single textile fabric or distributed over a plurality of such textile fabrics. Also, the fiber composite material may include a plurality of fabrics, some of which contain only reinforcing yarns and others contain additional or exclusive damping yarns. Finally, the design according to the invention of the fiber composite material can also be combined with the measure of the prior art described in which the fiber composite material or a component formed therefrom with at least one subsequently applied damping coating (eg made of a vulcanized polymer such as rubber, latex etc.) is provided.

According to one embodiment of the component, this has at least one, along the textile fabric area extending damping layer, Such a damping layer can, for. B. be interposed between two formed with damping threads fabric. In particular, a combination of at least one incorporated full-surface damping intermediate layer, which conventional reinforcing fibers, however, contains a particularly dampening selected matrix material (as described for example in the above-mentioned technical article), and the design of at least one textile fabric proposed here according to the invention conceivable. The areally extending damping layer may alternatively or additionally also form an outer layer (cover layer) of the component.

According to a further development, it is provided that a transparent matrix material is used for the production of the component and at least a part of the damping threads, in particular all damping threads have a different color or are colored differently colored than the reinforcing threads used in the same textile fabric. This results in a special visual design of the fiber composite material or of the component produced therewith. Other colored or suitably colored damping threads can thus for design purposes or z. B. also be provided for marking safety-related areas of components.

In a further development of the fiber composite material, it is provided that, in addition, the internal damping of the material is further increased by adding a so-called plasticizer into the relevant matrix system (eg epoxy resin system). The plasticizer is incorporated into the carrier resin. The matrix material produced thereby has a higher extensibility d. H. the elongation at break is increased. In the context of the invention, this also results in a further improvement of the mechanical damping properties of the fiber composite material or of the component produced therewith. In particular, a mixing ratio between resin and plasticizer (flexibilizer) can be chosen so that there is a noticeable increase in damping without significant loss of strength and z. B. Heat resistance comes.

The fiber composite material used in the component according to the invention can be used both for monolithic components, in particular planar components, as well as for individual layers of a fiber composite structure consisting of a plurality of layers.

So z. B. an inventive component are manufactured in sandwich construction, wherein at least one component layer is formed of a fiber composite material of the type described above. In a sandwich construction in the strict sense, d. H. with three layers, the fiber composite material described above z. B. form at least one of the two cover layers.

From the state of the art, sheet-like components produced in sandwich construction are known in which a honeycomb structure produced from pre-soaked (phenolic resin) paper is combined on both sides with flat CFK or GFK cover layers and impregnated with a matrix material to be cured.

According to the invention, such a sandwich component can be provided in which at least one of the conventional cover layers is replaced by a fiber composite material of the type described above, that is to say damping threads. Thus, the advantageously high specific strength of such a honeycomb structure can be combined with an increase in the damping properties (in particular with regard to vibrations and sound).

According to a development of such a modified sandwich component with honeycomb core is provided that the honeycomb core and at least one of the two outer layers are cured separately and are connected only after curing by means of a permanently elastic adhesive. For example, this is a suitably formulated epoxy adhesive film or an elastic silicone adhesive into consideration.

In practical experiments it has been shown that by such elastic decoupling at least one cover layer relative to the honeycomb core, the sound insulation of a sandwich panel can be significantly improved. This is probably due to the fact that with the elastic adhesive, an elastic layer is established, on the one hand a mechanical connection of the relevant cover layer or both cover layers done on the honeycomb core, but additionally the overall system (sandwich panel) damped due to the elastic property of the adhesive stronger than usual or decoupled vibrationally.

As this suitable elastic layer between the honeycomb core and at least one cover layer can, for. For example, a silicone adhesive of the type commercially available under the trade name "Naftoseal MC-780" can be used. In the prior art, this adhesive is usually used for sealing. The adhesive should remain elastic to decouple the honeycomb and topcoat. This is typically achieved by cross-linked, high-elasticity (ε >> 10%) elastomer-based adhesives.

For the preparation of such a sandwich component can, for. B. proceed as follows: First, an adhesive layer is formed on a flat field, for. B. by the adhesive, z. B. with a spatula, is passed on the field. Then the (preferably already cured or at least partially cured) honeycomb core is pressed with one of its flat sides in the adhesive field, so that the honeycomb structure is wetted at the corresponding contact lines with the adhesive. If appropriate, the same procedure is followed with the second flat side of the honeycomb core (if this is not to be connected in another way, eg by means of "co-bonding", or is already connected). The (preferably already at least partially cured) cover layer made of fiber composite material can then be pressed with relatively low pressure on the wetted with adhesive flat side of the honeycomb core and z. B. Be connected in the autoclave by thermal treatment with the honeycomb core. The amount of applied to the honeycomb core elastic adhesive may, for. B. be adjusted by appropriate training of the above adhesive field (eg., By appropriate choice of the shape and height of a tooth spatula used for spreading).

In the production of a textile fabric required for the invention, comprising damping threads, which preferably have increased elasticity and / or a viscous or viscoelastic property, practical difficulties may arise during introduction (eg braiding) of the damping threads, in particular due to higher friction and the eventual elasticity are conditional.

In order to avoid such difficulties, a method for producing a fabric for the production of a fiber composite material of the type described above may be used.

The manufacturing method not according to the invention is characterized in that at least two types of textile line structures which differ in their mechanical damping capacity are interwoven or intertwined, wherein the line structures having the increased damping capacity have a friction-reducing pretreatment prior to interweaving be subjected. As an alternative or in addition to the friction-reducing pretreatment, it can also be provided that during the weaving or braiding process, any line structure possessing the increased damping capacity, ie any "damping thread", not always as such but always with a "reinforcing thread" parallel to it (immediately adjacent thereto) is supplied.

With the non-inventive method can, for. B. at the moment of braiding or weaving the damping threads are ensured that the braiding or weaving process is unproblematic.

As a friction-reducing pretreatment z. B. may be provided by a suitable liquid or a powder pretreatment. For example, the damping threads used in the manufacture of the textile fabric can be passed through a corresponding liquid bath or powder bath (eg talcum powder, graphite, wax) as they are fed into a respective braiding or weaving station.

The components produced in this way can be used in many ways.

According to a preferred embodiment, use is provided as an interior space panel of a vehicle, in particular an aircraft (eg aircraft or helicopter). Alternatively, a use as a so-called skin field is also considered.

Advantageously results in comparison to the prior art for predetermined damping properties a lower height of such panels, often can be dispensed with an additional damping lining. As already mentioned above, the integrative solution provided with incorporated (eg braided or woven in) damping threads according to the invention saves the labor-intensive production steps of cutting and pasting damping additional coverings.

The lower height of vibration and / or sound-absorbing panels can, for. B. be advantageously exploited for the application of ceiling panels in helicopter cabins. In this case, the height is one for the panel Available space is often limited to 2 cm or less than 1.5 cm.

The use of panels produced according to the invention as a cabin lining, in particular a cabin ceiling panel, creates an improvement in the sound insulation for a given panel thickness.

The invention will be further described by means of embodiments with reference to the accompanying drawings. They show:

1 a top view of a fiber semis fabric with braided damping threads,

2 a schematic plan view of a planar fiber composite component according to an embodiment,

3 a schematic plan view of a flat fiber composite component according to another embodiment,

4 a schematic plan view (partially cut away) of a flat fiber composite component according to another embodiment (sandwich component), and

5 a sectional view taken along the line VV in 4 ,

1 shows a section of a textile fabric 10 , For example, a braid, which consists of two different types of textile line formations 12 and 14 is prepared and is provided as a semi-finished fiber material for producing a fiber composite material or fiber composite component.

For the production of the fiber composite material or fiber composite component, the in 1 illustrated braid 10 in a manner known per se, individually or stacked with other textile fabrics of this or another type or "draped", infiltrated with a liquid or viscous matrix material (eg epoxy resin system) optionally compacted and / or molded, and finally cured (eg. Thermally). For this purpose, all types of production technologies known per se from fiber composite technology can be used. Examples of this are transfer molding (RTM, "resin transfer molding"), vacuum infusion (eg VAP, VARI etc.) and their further developments (eg SLI, LRI, DP-RTM) etc.

The textile line formations 12 and 14 can each z. B. be formed as a thread or roving, wherein the material of the textile line formations 14 in comparison to the material of the line formations 12 has an increased mechanical damping capacity.

The textile line formations 14 with the increased mechanical damping capacity are therefore also referred to here for short as "damping threads" whereas the textile line formations 12 here also referred to as "reinforcing threads" for short.

The reinforcing threads 12 are formed in the illustrated embodiment as strip-shaped rovings of a few thousand quasi-endless carbon fibers. This roving has an approximately rectangular cross-section. Alternatively, the reinforcing threads could 12 also z. B. as a yarn or thread (in the strict sense) may be formed and made of other fibers such. As glass fibers, aramid fibers, etc. exist.

The damping threads 14 In the illustrated embodiment, each also formed as a roving of an approximately rectangular cross-section, however, consist of fibers with increased damping capacity, here z. From a plurality (e.g., several hundred) fibers of a vulcanized polymer (eg, rubber or the like).

That with one or more layers of the fabric 10 produced fiber composite material has an increased internal damping, so that for many applications advantageously the vibration and radiated sound are considerably reduced.

In general, suitable for forming the damping threads 14 in particular synthetic fibers which have an increased density and / or an increased elasticity and / or a viscous or viscoelastic property.

At the in 1 Example shown runs each damping thread 14 immediately adjacent a reinforcing thread 12 through the network 10 ,

In the following description of further embodiments, the same reference numerals are used for equivalent components, each supplemented by a small letter to distinguish the embodiment. In this case, essentially only the differences from the embodiment (s) already described are discussed and, moreover, reference is hereby explicitly made to the description of previous exemplary embodiments.

2 shows a planar component 20a , For example, for use as a soundproofing panel, which is formed in the illustrated embodiment as a whole as a fiber composite component with a matrix and embedded fibers, but this fiber composite material predominantly conventional (with reinforcing threads) and only in some areas 22a in the particular, already with reference to 1 is formed described manner.

In these subareas 22a contains the component 20a in each case at least one textile fabric 10a (preferably a multilayer stack of such sheets) in which a part of the textile line formations used has an increased mechanical damping capacity compared to the remaining textile line formations. Accordingly, any textile fabric can 10a z. B. from with reference to 1 each described sheet 10 be formed.

The subareas 22a are in the example shown on a two-dimensional grid over the surface of the component 20a distributed, in such a way that the subregions 22a each are located at those points when using the component 20a form antinodes in a vibration-prone instillation environment.

With the in 2 illustrated, only partial use of damping fiber material areas can thus vibrations with little impairment of the strength or rigidity of the component 20a be reduced.

At the in 2 represented component 20a are the damping trained sections 22a distributed distributed inside the component surface. Alternatively or additionally, these subregions may also be provided on the edge of a relevant component. An example of this is in 3 shown.

3 shows a planar component 20b with a peripheral area at the edge 22b containing the damping textile fabric 10b ,

Such a vibration damping at the edge of the component 20b is particularly advantageous for those applications in which the component 20b is connected at its edge with a supporting structure, such as a vehicle (including aircraft). A vibration or structure-borne sound transmission from the supporting structure to the component 20b is thus reduced efficiently.

Notwithstanding the examples according to the 2 and 3 Of course, the damping portions may also be provided both within the component surface and at one or more points of the component edge. In this regard, it should be remembered that there are also applications in which a connection of the planar component can alternatively or additionally involve attachment points which are located within the component surface.

4 shows a planar component 20c , made in sandwich construction of three layers, namely a honeycomb core 30c and on both sides with it glued cover layers 32c and 34c ,

At least one of the cover layers 32c . 34c is formed as a fiber composite material containing damping threads, so z. B. of the kind as already with reference to the 1 described.

The sectional view of 5 illustrates the connection of the upper and lower cover layers 32c and 34c each with an adhesive layer 36c respectively. 38c on the honeycomb core 30c ,

In the illustrated embodiment, the layers 30c . 32c and 34c each made of a fiber material and infiltrated prior to their bonding in each case with a synthetic resin and at least partially cured. As a fiber material is z. As cardboard suitable, but at least one of the outer layers 32c . 34c , Preferably both, as a fiber composite material containing damping threads are formed, ie z. B. of the kind as already with reference to the 1 described.

The adhesive layers 36c and 38c are each formed by an elastic silicone adhesive.

Claims (9)

Sheet-like component ( 20 ), at least partially made of a fiber composite material with a matrix and fibers, in the form of at least one of textile line formations ( 12 . 14 ) produced textile fabric ( 10 ) are embedded in the matrix, whereby a part of the line formations ( 14 ) compared to the remaining line formations ( 12 ) has an increased mechanical damping capacity, characterized in that the line formations ( 14 ) with the increased mechanical damping capacity only in certain component surface areas ( 22 ) or in these component surface areas ( 22 ) have a much higher proportion than in other component surface areas. Component ( 20 ) according to claim 1, wherein the sheet ( 10 ) is a tissue, a mesh or a scrim. Component ( 20 ) according to one of the preceding claims, wherein the line formations ( 12 . 14 ) are each formed as a thread or as a roving. Component ( 20 ) according to one of the preceding claims, wherein the remaining line formations ( 12 ) are formed of glass fibers, carbon fibers or aramid fibers. Component ( 20 ) according to one of the preceding claims, wherein the line structures possessing the increased damping capacity ( 14 ) are formed of fibers having an increased density and / or an increased elasticity and / or a viscous or viscoelastic property. Component ( 20 ) according to one of the preceding claims, wherein the line structures possessing the increased damping capacity ( 14 ) are formed of synthetic fibers. Component ( 20 ) according to one of the preceding claims, with at least one, along the textile fabric ( 10 ) areally extending damping layer. Component ( 20 ) according to one of the preceding claims, produced in sandwich construction. Use of a component ( 20 ) according to one of the preceding claims as Innenraumpaneel a vehicle, in particular aircraft.

Images